1. Field of the Invention
The present invention relates to a core of a dynamo-electric machine having a plurality of axially assembled core sub-parts and also relates to a dynamo-electric machine member having such a core and winding wires wound around the core.
2. Description of Related Art
In general, an armature of a dynamo-electric machine, such as a motor, includes a core, around which winding wires are wound. More specifically, the core includes a plurality of radially extending teeth, and the winding wires are wound around the corresponding teeth. One such core disclosed, for example in Japanese Unexamined Patent Publication No. 9-46941, includes a plurality of core sub-parts, which are axially assembled together to form the core. In such a core, circumferentially adjacent teeth of the core are separately provided into the different core sub-parts, so that, for example, one of any two adjacent teeth of the core is provided in one of the core sub-parts, and the other one of the two adjacent teeth is provided in another one of the core sub-parts. In assembly of the core, winding wires are wound around the two adjacent teeth of the core, respectively, while the core sub-parts of the core, which include the two adjacent teeth, respectively, are separated from one another to separate the two adjacent teeth from one another. Thereafter, the core sub-parts are assembled together to form the core. In this way, the adjacent teeth do not interfere with each other in the winding operation of the wires therearound.
In the above motor, two circumferential ends of a tooth main body of each tooth are parallel to an assembling direction of the tooth, i.e., an axial direction of the core. In the above motor, a circumferential space between extended portions of two adjacent teeth, each of which extends circumferentially from a radially outer end of the tooth main body of the corresponding tooth, is relatively large, so that relatively large cogging torque is generated. Furthermore, in the above motor, when a circumferential space between any two adjacent ones of the wires is reduced or when the two adjacent ones of the wires are engaged with one another at a predetermined pressure to increase a space factor of the wires, damage to the wires (e.g., a damage to an insulating film of the wire) could occur due to strong frictional engagement between the wires during a long axial relative movement of the core sub-parts (from an initial stage to a late stage of the axial assembly of the core sub-parts). This would result in short-circuiting between the wires and/or a reduction in yield of the dynamo-electric machines.
Furthermore, in the above core, when the core sub-parts are axially assembled together to form the core, parallel fitting wall surfaces, which are parallel to the axial direction of the core, of a fitting recess (fitting portion) of one of the core sub-parts are engaged with parallel fitting wall surfaces, which are parallel to the axial direction of the core, of a corresponding fitting projection (fitting portion) of another one of the core sub-parts. In a case where the core sub-parts are made by compression molding of magnetic powder, when the core sub-parts are axially assembled together, portions, such as the fitting portions, of the core sub-parts contact, i.e., collide with one another. This may result in cracking or chipping of the core sub-parts. In order to prevent the collision of the core sub-parts, it is conceivable to increase a space between the opposed parallel fitting wall surfaces of the core sub-parts. However, the increase in the space between the opposed parallel fitting wall surfaces disadvantageously causes an increase in magnetoresistance at the space between the opposed parallel fitting wall surfaces. This causes a reduction in efficiency of the motor, which has the above core.